Optimal eastern cottontail habitat includes open grassy areas, clearings, and old fields supporting abundant green grasses and herbs, with shrubs in the area or edges for cover.[7] The essential components of eastern cottontail habitat are an abundance of well-distributed escape cover (dense shrubs) interspersed with more open foraging areas such as grasslands and pastures.[8] Habitat parameters important for eastern cottontails in ponderosa pine, mixed species, and pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands include woody debris, herbaceous and shrubby understories, and patchiness. Typically eastern cottontails occupy habitats in and around farms including fields, pastures, open woods, thickets associated with fencerows, wooded thickets, forest edges, and suburban areas with adequate food and cover. They are also found in swamps and marshes and usually avoid dense woods. They are seldom found in deep woods.[3]

The eastern cottontail home range is roughly circular in uniform habitats. Eastern cottontails typically inhabit one home range throughout their lifetime, but home range shifts in response to vegetation changes and weather are common.[8] In New England eastern cottontail home ranges average 1 hectare (1.4 acres) for adult males and 0.5 hectares (1.2 acres) for adult females but vary in size from 0.2 to 16.2 hectares (0.5 to 40 acres), depending on season, habitat quality, and individual. The largest ranges are occupied by adult males during the breeding season. In southwestern Wisconsin adult male home ranges averaged 3 hectares (6.9 acres) in spring, increased to 4 hectares (10 acres) in early summer, and decreased to 1 hectare (3.7 acres) by late summer.[9] Daily activity is usually restricted to 10% to 20% of the overall home range.[8]

In southeastern Wisconsin home ranges of males overlapped by up to 50%, but female home ranges did not overlap by more than 25% and actual defense of range by females occurred only in the immediate area of the nest. Males fight each other to establish dominance hierarchy and mating priority.[9]

Eastern cottontails forage in open areas and use brush piles, stone walls with shrubs around them, herbaceous and shrubby plants, and burrows or dens for escape cover, shelter, and resting cover. Woody cover is extremely important for the survival and abundance of eastern cottontails.[8] Eastern cottontails do not dig their own dens (other than nest holes) but use burrows dug by other species such as woodchucks.[3] In winter when deciduous plants are bare eastern cottontails forage in less secure cover and travel greater distances.[8] Eastern cottontails probably use woody cover more during the winter, particularly in areas where cover is provided by herbaceous vegetation in summer.[10] In Florida slash pine flatwoods, eastern cottontails use low saw-palmetto (Serenoa repens) patches for cover within grassy areas.[11]

In nest, under production

Most nest holes are constructed in grasslands (including hayfields).[8] The nest is concealed in grasses or weeds. Nests are also constructed in thickets, orchards, and scrubby woods.[3] In southeastern Illinois tall-grass prairie, eastern cottontail nests were more common in undisturbed prairie grasses than in high-mowed or hayed plots. In Iowa most nests were within 64 m (70 yd) of brush cover in herbaceous vegetation at least 10 cm (4 in) tall. Nests in hayfields were in vegetation less than 20 cm (8 in) tall. Average depth of nest holes is 13 cm (5 in), average width 13 cm (5 in), and average length 18 cm (7 in). The nest is lined with grass and fur.[10][12]

The eastern cottontail is chunky red-brown or gray-brown in appearance with large hind feet, long ears and a short fluffy white tail. Its underside fur is white. There is a rusty patch on the tail. Its appearance differs from that of a hare in that it has a brownish-gray coloring around the head and neck. The body is lighter color with a white underside on the tail. It has large brown eyes and large ears to see and listen for danger. In winter the cottontail's pelage is more gray than brown. The kits develop the same coloring after a few weeks, but they also have a white blaze that goes down their forehead; this marking eventually disappears. This rabbit is medium-sized, measuring 36–48 cm (14–19 in) in total length, including a small tail that averages 5.3 cm (2.1 in).[13][14] Weight can range from 800 to 2,000 g (1.8 to 4.4 lb), with an average of around 1,200 g (2.6 lb). The female tends to be heavier, although the sexes broadly overlap in size.[15][16] There may be some slightly variation in the body size of Eastern cottontails, with weights seeming to increase from south to north, in accordance with Bergmann's rule. Adult specimens from the Florida Museum of Natural History, collected in Florida, have a mean weight of 1,018 g (2.244 lb).[17] Meanwhile, 346 adult cottontails from Michigan were found to have averaged 1,445 g (3.186 lb) in mass.[18]

The eastern cottontail is a very territorial animal. When chased, it runs in a zigzag pattern, running up to 29 km/h (18 mph). The cottontail prefers an area where it can hide quickly but be out in the open. Forests, swamps, thickets, bushes, or open areas where shelter is close by are optimal habitation sites for this species. Cottontails do not dig burrows, but rather rest in a form, a shallow, scratched-out depression in a clump of grass or under brush. It may use the dens of groundhogs as a temporary home or during heavy snow.[19]

Eastern cottontails are crepuscular to nocturnal feeders; although they usually spend most of the daylight hours resting in shallow depressions under vegetative cover or other shelter; they can be seen at any time of day.[12] Eastern cottontails are most active when visibility is limited, such as rainy or foggy nights.[3] Eastern cottontails usually move only short distances, and they may remain sitting very still for up to 15 minutes at a time. Eastern cottontails are active year-round.[12]

The onset of breeding varies between populations and within populations from year to year. The eastern cottontail breeding season begins later with higher latitudes and elevations. Temperature rather than diet has been suggested as a primary factor controlling onset of breeding; many studies correlate severe weather with delays in the onset of breeding.[20] In New England breeding occurs from March to September. In New York the breeding season occurs from February to September, in Connecticut from mid-March to mid-September. In Alabama the breeding season begins in January. In Georgia the breeding season lasts 9 months and in Texas breeding occurs year-round.[12][20] Populations in western Oregon breed from late January to early September.[20] Mating is promiscuous.[3]

The nest is a slanting hole dug in soft soil and lined with vegetation and fur. The average measurements are: length 18 cm (7.09 in), width 12 cm (4.9 in), and depth 12 cm (4.71 in).[10] The average period of gestation is 28 days, ranging from 25 to 35 days.[12] Eastern cottontail young are born with a very fine coat of hair and are blind. Their eyes begin to open by 4 to 7 days. Young begin to move out of the nest for short trips by 12 to 16 days and are completely weaned and independent by 4 to 5 weeks.[10][21] Litters disperse at about 7 weeks. Females do not stay in the nest with the young but return to the opening of the nest to nurse, usually twice a day.[12][21]

Reproductive maturity occurs at about 2 to 3 months of age. A majority of females first breed the spring following birth; but 10% to 36% of females breed as juveniles (i.e., summer of the year they were born).[22] Males will mate with more than one female. Female rabbits can have 1 to 7 litters of 1 to 12 young, called kits, in a year; however, the average number of litters per year is 3–4 and the average number of kits is 5.[14] In the South female eastern cottontails have more litters per year (up to 7) but fewer young per litter.[12][20] In New England female eastern cottontails have three or four litters per year. The annual productivity of females may be as high as 35 young.[12][21]

The diet of eastern cottontails is varied and largely dependent on availability. Eastern cottontails eat vegetation almost exclusively; arthropods have occasionally been found in pellets.[23] Some studies list as many as 70[23] to 145 plant species in local diets. Food items include bark, twigs, leaves, fruit, buds, flowers, grass seeds, sedge fruits, and rush seeds.[10] There is a preference for small material: branches, twigs, and stems up to 0.64 cm (0.25 in). Leporids including eastern cottontails are coprophagous, producing two types of fecal pellets, one of which is consumed. The redigestion of pellets greatly increases the nutritional value of dietary items.[10][12]

In Kansas the largest cause of mortality of radiotracked eastern cottontails was predation (43%), followed by research mortalities[clarification needed] (19%), and tularemia (18%). A major cause of eastern cottontail mortality is collision with automobiles. In Missouri it was estimated that 10 eastern cottontails are killed annually per mile of road. The peak period of highway mortality is in spring (March through May); roadside vegetation greens up before adjacent fields and is highly attractive to eastern cottontails.[22]

Annual adult survival is estimated at 20%. Average longevity is 15 months in the wild; the longest lived wild individual on record was five years old. Captive eastern cottontails have lived to at least nine years of age.[12]

The Eastern Cottontail has to contend with many predators, both natural and introduced. Due to their often large populations in Eastern North America, they form a major component of several predators' diets. Major predators of eastern cottontail include domestic dogs (Canis lupus familiaris), foxes (Vulpes and Urocyon spp.), coyote (C. latrans), bobcat (Lynx rufus), domestic cat (Felis catus), weasels (Mustela spp.), raccoon (Procyon lotor), mink (M. vison), great horned owl (Bubo virginianus), barred owl (Strix varia), hawks (principally Buteo spp.), corvids (Corvus spp.), and snakes.[3]

Predators that take nestlings include raccoon, badger (Taxidea taxus), skunks (Mephitis and Spilogale spp.), and Virginia opossum (Didelphis virginiana).[22] In central Missouri eastern cottontails comprised the majority of biomass in the diet of red-tailed hawks (Buteo jamaicensis) during the nesting season. In Pennsylvania the chief predator of eastern cottontails is the great horned owl.[22] In the Southwest cottontails including eastern cottontail comprise 7 to 25% of the diets of northern goshawk (Accipiter gentilis). In Texas eastern cottontails are preyed on by coyotes more heavily in early spring and in fall than in summer or winter. In southwestern North Dakota cottontails (both eastern and desert cottontail Sylvilagus auduboni) were major prey items in the diets of bobcats.[24]